1. Field of the Invention
The present invention relates to a liquid crystal display (LCD) device using a dispensing method, and more particularly, to a method of fabricating a liquid crystal display device capable of improving image quality by preventing gravity defects in liquid crystal display.
2. Description of the Background Art
With the recent development of various portable electronic devices such as a mobile phones, PDAs, notebook computers, light and thin flat panel display devices are increasingly demanded. Research is actively ongoing on such flat panel display devices including liquid crystal displays (LCDs), plasma display panels (PDPs), field emission displays (FEDs), vacuum fluorescent displays (VFDs) and the like. Of those devices, the LCD devices are drawing much attention because of the ability to be mass produced, the relatively easy operation of their driving units, and their implementation of high image quality.
FIG. 1 is a schematic cross-sectional view of a general LCD device. As illustrated in the drawing, an LCD device 1 includes a lower substrate 5, an upper substrate 3, and a liquid crystal layer 7 formed between the lower and upper substrates 5 and 3. The lower substrate 5 is a driving device array substrate. Although not illustrated in the drawing, a plurality of pixels are formed on the lower substrate 5, and a driving device, such as a thin film transistor (TFT) is formed in each pixel. The upper substrate 3 is a color filter substrate and includes a color filter layer for implementing actual colors. Also, a pixel electrode and a common electrode are formed on the lower substrate 5 and the upper substrate 3, respectively, and alignment layers are applied thereon to align liquid crystal molecules of the liquid crystal layer 7.
The lower substrate 5 and the upper substrate 3 are bonded together by a sealing material 9, and the liquid crystal layer 7 is formed therebetween. Thus, the liquid crystal molecules are driven by the driving device formed on the lower substrate 5 to control the transmittance of light passing through the liquid crystal layer, thereby displaying information.
A process of fabricating an LCD device may be divided into a driving device array substrate process for forming driving devices on the lower substrate 5, and a color filter process and a cell process for forming a color filter on the upper substrate 3. Such processes for the LCD will now be described with reference to FIG. 2.
In the driving device array process, a plurality of gate lines and data lines are arranged on the lower substrate to define pixel areas, and a TFT (for example) connected to the gate and data lines is formed in each of the pixel areas (S101). Also, in the driving device array process, a pixel electrode is formed that is connected to the TFT to drive the liquid crystal layer upon receiving signals through the TFT.
Also, in the color filter process, a red, green and blue (RGB) color filter layer and common electrodes are formed on the upper substrate 3 (S104).
Then, alignment layers are applied on the upper and lower substrates 3 and 5, respectively, and then the alignment layers are rubbed to provide an alignment controlling force or a fixing surface (i.e., a pretilt angle and an alignment direction) to the liquid crystal molecules of the liquid crystal layer formed between the upper and lower substrates 3 and 5 (S102, S105). Thereafter, spacers are dispersed onto the lower substrate to maintain a uniform cell gap, a sealing material is applied along an outer edge of the upper substrate 3, and then the lower and upper substrates 5 and 3 are pressurized and bonded (S103, S106, S107).
The bonded lower substrate 5 and the upper substrate 3 are formed form large-sized glass substrates. That is, a plurality of panel regions are formed in each large-sized glass substrate, and a TFT and a color filter layer are formed in such panel regions, respectively. For this reason, in order to fabricate each individual liquid crystal panels, the glass substrates should be cut and processed (S108). Thereafter, a liquid crystal is injected through a liquid crystal injection hole into each liquid crystal panel processed in the aforementioned manner to form the liquid crystal layer. Then, the liquid crystal injection hole is encapsulated or “plugged”, and then the liquid crystal panel is examined, thereby fabricating an LCD device (S109, S110).
Here, the injecting of the liquid crystal is achieved by the following processes. That is, as illustrated in FIG. 3, a nitrogen gas (N2 gas) is supplied into a vacuum chamber in a state where an injection hole 16 of a liquid crystal panel 1 is in contact with the liquid crystal, and thus a degree of vacuum of the chamber 10 is lowered. Then, the liquid crystal 14 is injected into the panel 1 by the difference between the internal pressure of the liquid crystal panel 1 and the pressure of the vacuum chamber 10. After the panel 1 is completely filled with the liquid crystal, the injection hole 16 is encapsulated by an encapsulating material, thereby forming a liquid crystal layer (This type of injection method is called a vacuum injection method of liquid crystal).
However, disadvantageously, it takes a long time to inject liquid crystal into a panel through the injection hole 16. That is, only a very small amount of liquid crystal is injected into the liquid crystal panel per unit time because this is only a very small gap of just a few micrometers (μm) between the driving device array substrate and the color filter substrate of the liquid crystal panel. For example, when a liquid crystal panel of approximately 15 inches is fabricated, it takes approximately 8 hours to complete the injection of liquid crystal. Such injection of liquid crystal over a long period of time delays the fabrication process of the liquid crystal panel, and thus deteriorates fabrication efficiency. Particularly, the vacuum injection method is inadequate for a large-sized liquid crystal panel because the time it takes to inject liquid crystal increases as liquid crystal panels become larger.